The present invention relates to a filter for an aquarium.
More particularly it relates to a filter for an aquarium which has a housing with a bottom chamber and at least one filter compartment with a filter material, a water supply for supplying water from above into the filter compartment so that the water passes at least one filter compartment and is supplied to the bottom chamber, and then aspirated from the bottom chamber by a pump and recirculated back to the aquarium through a conduit.
Filters of the above mentioned general type are known in the art. One of such filters is disclosed for example in the German Patent 2,700,030 and operates as an alternating lifting-lowering filter. This filter is formed as an outer filter and connected through a supply conduit with the aquarium tank. The filter has only one filter compartment. The supply is performed from above into a space above the filter compartment. Under the filter compartment there is a bottom chamber, and a reverse U-shaped conduit opens with its free end into the bottom chamber. A pump is connected with the conduit, aspirates water accumulated in the bottom chamber and supplies it back through a return conduit leading to the aquarium tank Furthermore, for safety reasons for the case of a clogging of the filter compartment between the upper space with the supply and the bottom chamber, a bypass conduit is provided and operates so that when the filter compartment is clogged the upwardly supplied water flows directly through the bypass conduit downwardly into the bottom chamber. The aspiration of the water is performed always in the region of the bottom chamber through the open end of the U-leg located there. During the aspiration cycle the water level lowers in the filter compartment downwardly. The discharge quantity per time unit is greater than the supply quantity per time unit. Due to this design a well know lifting-lowering operation of the filter is obtained. The filter however is complicated with respect to the devices for actuating the lifting-lowering function since the reverse U-shaped pipe connected to the pump extends in the filter mass of the filter compartment with its both legs.